A sizable number of the cables used for telecommunication purposes and for electrical power transmission are buried below ground. Underground burial of cable, while more costly than stringing cable above ground on poles or towers, nevertheless affords certain advantages. Burial of cable below ground is more aesthetically pleasing and reduces the risk of cable damage due to lightning and other elements. On the other hand, a buried cable is far more susceptible to damage by digging due to construction or the like.
To reduce the risk of an underground cable being severed or otherwise becoming damaged as a result of nearby digging, most utilities a have a strict policy requiring that any buried cable in the vicinity of such digging be physically located. To physically locate a buried cable, a utility worker usually must excavate the earth at spaced locations along the cable to expose the cable in order to verify its exact location. Each such excavation is referred to as a "pothole."
The starting location of each such pothole is obtained by first establishing the approximate location of the cable. While a map may be helpful to locate the cable generally, a more exact location is obtained by injecting a Radio Frequency (RF) signal into the cable and then sensing the RF energy that is radiated using an RF receiver for this purpose. The amount of RF energy that is sensed increases as the proximity of the cable to the receiver increases. However, RF sensing by itself does not provide a way of establishing the exact location of the cable since electrical interference from other cables located close to the cable of interest may cause a false measure of RF energy.
Thus, the only accurate way to locate and identify a buried cable is to dig a series of potholes to expose portions of the cable along its length. Depending on the particular utility policy of how far apart such potholes should be, and the extent of the digging that is to occur near the cable, a large number of such potholes may be necessary. As may be appreciated, the process of digging each required pothole is time consuming and extremely expensive.
Thus, there is a need for a technique for locating and identifying a cable, and particularly, a buried cable, with reduced effort and expense.